75% is kind of high for long term care, but I know that you were just guessing at that number. 50-60% is more what I aim for during the maintenance season. That number will go way up during the rainy season if I am trying to breed pairs. It may also go way down during the warm season when I may slightly brumate them. Again, this is for adults who are cycling. For babies, just stick to the simple constant temps (75-80F) and constant humidity(50-60%) and keep them both very mild. Too wet and they will get respiratory infections (RI) and if they are too dry they can get RI or dessicate on you. They will be fine without a nighttime drop, too, if you like.
I like using pinky hams with babies because it's easier to make them hold onto it when they strike. With a full pink there is enough weight there that they can just sling it off. With a ham, there is less mass and they have a harder time spitting it out. Be more aggressive if your babies aren't striking. Get mad and make that baby eat. Bump them on the neck and tail and get them riled up and don't take no for an answer. But do it in brief sessions so as to not tire the snakes out too much. Try for 60 seconds and then give them a rest. Most people are too gentle in the beginning...I know that I was. Just find that happy median between too gentle and abuse. It's harder in the beginning, but it will get easier with every feed. Good luck.
Derek Morgan